The spec:

  describe "rss action" do
    before :each do
      get :rss
    end
    
    it "should turn off session management" do      
      request.session_options.should be_false
    end    
    
  end

 # turn off session management for only the atom and rss actions.
  session :off, :only => %w(atom rss)
  def rss
    # ...  
  end